The preferred embodiments of the present invention relate to an RF access control system for controlling access to an access point. More specifically, the preferred embodiments of the present invention relate to a method and system for driving a motor of a motor-driven locking subsystem of an access control system in such a way as to save battery power of the motor-driven locking subsystem and ensure security.
A wireless access control system may provide several advantages over a traditional, wire-based access control system. In a traditional, wired access control system, each access point, such as a door, for example, is equipped with a locking module to secure the access point. Each locking module is in turn directly wired to a remote access control module. The access control module is typically a database that compares a signal received from the locking module to a stored signal in the database in order to determine an access decision for that locking module. Once the access decision has been determined by the access control module, the decision is relayed to the locking module through the wired connection.
The use of wired connections between the access control module and the locking module necessitates a large investment of time and expense in purchasing and installing the wires. For example, for larger installations, literally miles of wires must be purchased and installed. An access control system that minimizes the time and expense of the installation would be highly desirable.
Additionally, wire-based systems are prone to reliability and security failures. For example, a wire may short out or be cut and the locking module connected to the access control module by the wire may no longer be under the control of the access control module. If a wire connection is cut or goes, the only alternative is to repair the faulty location (which may not be feasible) or run new wire all the way from the access control module to the locking module, thus incurring additional time and expense. Conversely, an access control system that provides several available communication channels between the locking module and the access control module so that if one communication channel is not usable, communication may proceed on one of the other communication channels, would also be highly desirable, especially if such an access control system did not add additional costs to install the additional communication channels.
A wireless access system providing a wireless communication channel between the locking module and the access control module may provide many benefits over the standard, wire-based access control system. Such a wireless access system is typically less expensive to install and maintain due to the minimization of wire and the necessary installation time. Additionally, such a system is typically more secure because communication between the locking module and the access control module is more robust that a single wire.
However, one difficulty often encountered in installing and maintaining such a wireless access system is providing power to the individual, remote locking modules. For example, such locking modules may be powered by battery, but standard locking modules for wire-based access control systems are typically quite wasteful of power, a commodity in short supply in wireless access systems. Consequently, a motor driving the locking mechanism of the locking module that is power efficient is highly desirable.
Typically, the motor of a battery powered locking subsystem is driven at or near full power until the locking mechanism is fully locked or fully unlocked. The conditions of being fully locked or fully unlocked are typically detected by some mechanical or electro-mechanical feedback such as a conventional limit switch. This type of feedback mechanization adds components and cost to the subsystem. Driving the motor in this way requires a great deal of stored energy to lock and unlock the mechanism. This drains the battery at a fast rate, yielding a reduced number of times that a door with such a locking mechanism may be locked and unlocked before the battery needs to be changed or recharged.
Consequently, a simple, cost effective approach to driving the motor of a battery powered locking subsystem in such a fashion as to conserve battery life would be highly desirable.